Encapsulated optocomponents with associated wave guides, connection devices, etc. are at present expensive, which is an obstacle for a more widespread introduction of the optical communication technology. One of the major reasons for the high component cost is the extreme requirements on mechanical precision in the alignment of an optoelectronic component with a waveguide and of a waveguide in a component with another waveguide. The mounting methods of today do not allow electronic circuits to be contained or housed, in a functional and efficient manner, in the package and/or be mounted efficiently together with the optoelectronic component on a circuit board.
Having access to a common "micro construction method" for optical and microelectronic devices the conditions would be improved in order to allow fabrication of optical transmitter and receiver modules at a low cost, thereby opening new applications and markets for optical communication.
At present an intensive development work within the microstructure technology is pursued in order to achieve a possible way of positioning devices with an accuracy of the magnitude of order of one micrometer. One of the aims of this work is to replace the costly details, which are today used in the mounting of optocomponents, with mass produced details of for instance silicon.
In parallel there is a development towards more efficient methods for mounting and encapsulating integrated optical devices. One obvious development path is the use of polymer films, usually polyimide films, for this object. Since production of conductive leads using coating and etching can be carried out on such films and sandwich constructions having several layers comprising electrical conductors and ground planes ("multilayer technique") are used, making impedance matching possible, several chips can be mounted together with each other having no additional demands on substrates or base materials. Moreover, when encapsulated with resin such a polymer film can take over the function of the traditional lead frame made of thin metal plate. Metallic or possibly metallized connection legs may protrude from the capsule wall from the carrier film in order to accomplish the electrical connection of the electronic circuits to the exterior. Also exterior metallized surfaces like those used in TAB-mounting can be present.
Flexible resin tape having lead portions can be used in an electronic multichip package as disclosed in U.S. Pat. No. 5,245,215. The flexibility of the tape is primarily used for allowing a dense packing of the chips.
In the International patent applications PCT/SE95/00281, filed on Mar. 20, 1995, PCT/SE95/01232, filed on Oct. 19, 1995, and PCT/SE95/01233, filed on Oct. 19, 1995 for the same applicant/assignee methods for encapsulating optoelectrical components with resin or plastic materials at a low cost are described. The methods rely on the fact that a substrate for hybrid mounted optocomponents is positioned with a high accuracy in a mould cavity to be overmoulded with plastics. The optocomponent is encapsulated by means of transfer moulding, whereby an optical interface in the capsule wall is obtained simultaneously by means of V-grooves on the substrate and guide pins in the mould. An electrically conducting lead frame can be used for establishing electrical contact with the electronic circuits. The lead frame usually consists of a punched or etched metal detail, for instance a thin copper or aluminium sheet.
Simultaneous encapsulation, with plastics, of optocomponents and electronic circuits with a positioning of waveguides and optoelectrical components on substrates of silicon is previously known.
Thus, in the published European patent application EP-A1 0 600 645 an optoelectronic module encapsulated with plastics and of SIP type ("Single In-line Package") is disclosed comprising electronic components and optocomponents placed on a silicon substrate.
In the published European patent application EP-A2 0 596 613 a coupling module for coupling optical fibres 6 to an "optical unit", or rather to an "electronic part" through an "optical unit" is described. The optical unit may comprise a base 13 of possibly silicon having electrodes and microlenses 4a and photodetectors 4, see FIGS. 6a-7b. The optical unit is connected to the electronic part, which can be an integrated semiconductor circuit, for instance by means of wire bonding between the electrodes on the support base plate 13 and conductive areas 9a on the electronic part 9 (FIGS. 5a and 5b). However, this coupling module is not encapsulated with plastics.